Broadcasting information about eligible network operators to mobile user equipments

ABSTRACT

The invention proposes a system and method for providing an attachment or a connection in a communication network. A connection is established between a user equipment and another network element via a radio access network, and one or more of alternatively selectable support network elements of at least two operator networks, the radio access network element broadcasting information on types of support network elements of available operator networks to the user equipment.

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to a system and method for providing anattachment or connection in a communication network. The communicationnetwork may be a pure data network, a network for transmitting dataand/or other non-data type of information such as speech, or may be anetwork exclusively reserved for non-data information. The network canbe a circuit-switched network, a packet-switched network such as a GPRSor UMTS network, or may consist of a combination of networks ofdifferent type.

When providing a connection in a communication network, usually severalnetwork elements are involved, including the connection originatingnetwork element, the connection terminating network element and/or oneor more intermediate network elements such as a base station, a basetransceiver station, a base station controller and/or one or moresupport nodes handling the signalling and/or user traffic.

As an example, in a GPRS-based or UMTS-based network, a connection (e.g.call) originating from, or terminating at, a user equipment (UE) such asa fixed or mobile equipment or mobile station (MS) is made to aconnection terminating or originating equipment using a radio networkcontroller (RNC) which communicates with a support entity such as a SGSN(Serving GPRS Support Node) and possibly a GGSN (Gateway GPRS SupportNode). The connection terminating and originating equipments can belocated in the same or a different network. In particular, in case ofmobile user equipments, the actual location thereof is defined with aresolution of a routing area (e.g. in idle state) or with a finerresolution of a cell (e.g. when handling a connection such as a call).Note that Routing Area (RA) is a standard term used in conjunction withGPRS, while GSM and UMTS circuit-switched systems use the term LocationArea (LA). In both cases, the area is referring to the area where amobile station is registered in the serving node (e.g SGSN or MSC/VLR),and where eventually the serving node pages the mobile station toestablish connection. In this application, the term area will be used torefer to location area and/or routing area.

The coverage area of an entire network is usually divided into severalareas (RA or LA), with one area (in a GPRS-or UMTS-based network) beingassigned to one serving node (one serving node typically handling manyareas). When having information on the area where the user equipment ispresently located, the serving node in charge of handling a connectionto or from this user equipment is unambiguously defined.

For example, in GSM and UMTS, this one-to-one correlation between therouting or location areas and the assigned SGSNs or MSC/VLRs may,however, be of disadvantage e.g in case of break-down of an SGSN or anMSC/VLR or necessary maintenance operations such as software updating.In such a case, the routing area or the location area has to becompletely shut-down and is at least temporarily no longer usable forproviding connections.

This situation may be significantly improved when changing the networkstructure in such a manner that at least two serving nodes such as twoSGSNs or two MSC/VLRs are able to handle the same routing or locationarea. In such a case, e.g. a base station controller (BSC) or radionetwork controller (RNC) may use different interfaces to the servingnodes such as Iu and/or Gb and/or A.

The provision of two or more support nodes serving the same areaprovides several advantages such as resilience by enabling an RNC(possibly having a list of available SGSNs) to use another SGSN if thepreviously used SGSN should become overloaded or out of order.Furthermore, maintenance operations such as software updates can beeffected without shutting down the area. In addition, the networksignalling caused by inter-SGSN handovers can be reduced.

As an example, several SGSNs may be provided for covering a metropolitanarea such as London area, and a mobile station moving around the citycan always use its-original SGSN for handling connections.

For instance, an IP network may be introduced on an interface such as Iuinterface which presently is mainly used as a point-to-point Iuinterface between the RNC and the SGSN. When introducing an IP networkor network of some other appropriate type on the Iu interface, one RNCmay be connected to several SGSNs.

In a case where one network element (which e.g. is in charge ofcontrolling the radio connection to a user equipment) is able to connectto different support nodes being alternatively provided, there exists aproblem in finding and selecting an appropriate support node, forinstance an SGSN to be used for a signalling connection. This signallingconnection may e.g. be used to transfer L3 (layer 3) messages (such asmobility management MM and session management SM) between the userequipment (e.g. MS) and the support nodes such as SGSN. Furthermore, incase of inter-support node location update the new support node wouldbenefit from finding the old support node which was serving the userequipment until location update. Note that in UMTS, handover (i.e.serving RNS relocation) happens so that the old node selects a new node.In location update, the new node has to find the old node e.g. to get MMand PDP contexts of the UE. In GPRS/UMTS, location update=routing areaupdate.

SUMMARY OF THE INVENTION

The present invention provides a solution for solving or at leastrelieving the above problems either partly or entirely.

According to one aspect, the invention provides a system as defined inclaim 1. This system may consist of a whole network, may be only a partof a network, or may comprise two or more networks.

According to a further aspect, the invention provides a method asdefined in the independent method claim.

According to a preferred aspect of the invention, the radio accessnetwork is adapted to broadcast, to the user equipment(s), informationon available operator network(s) or support network element(s), whereinthe broadcast information includes information on the generation type ofthe support network elements. The user equipment is adapted to receivethe broadcast information and to send selection information to the radioaccess network for selecting an operator network and/or a supportnetwork element.

In a preferred embodiment, a UE is adapted to select from differentnetwork operators which parallely provide attachment and connectionservices for establishing calls or other types of connections.

The broadcast information may include area identifiers of the operatornetworks, preferably Location or Routing Area Identifiers (LAIs/RAIs) ormobile country codes and/or mobile network codes of the operatornetworks, and/or identifiers for identifying available support networkelements. The broadcast information also includes information on thegeneration type of the support network elements. In a preferredimplementation, the user equipment is preferably adapted to receive onlythat part of broadcast information which is intended for the generationtype of the user equipment.

The RNC/BSC may broadcast multiple area identifiers per cell. Every areaidentifier preferably includes the mobile network code to identify thecore network operator.

The support network elements can be serving nodes, preferably SGSNs. Theradio access network element can be a Radio Network Controller or a BaseStation Controller.

At least one of the network elements, e.g. a radio network controller ora base station controller or a DNS server, preferably stores a list ofsupport network elements of the operator networks, said list includinginformation on the generation type of support network elements and beingaccessible by the radio access network using an identifier identifyingan area and/or an identifier identifying a mobile network code, or adesired support network element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a basic structure of one embodiment of a system inaccordance with the invention;

FIG. 2 illustrates the message flow for establishing a connectionbetween a user equipment and a serving node of a selected operator;

FIG. 3 shows steps of another method for selecting a serving node of adesired operator;

FIGS. 4 and 5 illustrate message flows in system and methods accordingto further embodiments of the invention; and

FIG. 6 illustrates a list of available support entities.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows the basic structure of an embodiment of a system inaccordance with the invention. The system includes two or more networks1, 1′, or forms a part thereof. The network 1 can connect to at leastone, or usually a plurality of, user equipments (UE) 2 which, in thisembodiment, are implemented as mobile stations. The user equipments mayalso be of any other type of equipments such as stationary terminals.Although only one user equipment 2 is shown, usually several userequipments are attached to the network 1 and represent connectionoriginating or terminating equipments.

In case of connection, or connection set-up, with another equipmentforming part of network 1 or of another network, a radio connection touser equipment 2 is provided and handled by a radio access network(RAN). The RAN comprises, in this embodiment, a radio network controller(RNC) 3 which is part of, or represents, the radio access network forradio connection to user equipment 2. Usually, several radio accessnetworks and controllers 3 may be provided in the networks 1, 1′ forradio coverage of the different areas of the networks 1, 1′. The RNC 3(first network element) may be selectively connected to differentserving entities, e.g. nodes which, in this embodiment, are implementedas SGSNs (Serving GPRS Support Nodes) 4, 4′, 6, and 6′.

The network may comprise additional or alternative serving nodes such asmobile switching centres (MSCs) which normally will be combined withvisitor location registers (VLRs). The serving nodes 4, 4′, 6, 6′ may beconnected, if necessary, to a gateway node which can be implemented asGGSN (Gateway GPRS Support Node) 5 and provides the possibility ofconnection to other networks.

In addition, a DNS (Domain Name System) server 7 may be provided whichmay form part of network 1 or may be a network-external component. TheDNS server 7 can be accessed by RNC 3, and usually also by other networkcomponents such as serving nodes 4, 6 and/or gateway node 5. Thecommunication possibilities are shown in FIG. 1 by means ofdouble-headed arrows.

The invention additionally provides, according to a further aspect, oneor more network elements equipped so as to implement the hardwarestructure or functions usable in a network or connection or selectionmethod as defined in the claims and/or described in the presentspecification.

The present invention provides a solution for allowing a UE to decide onan operator to be used, wherein a radio access network element such as aradio network controller or base station controller can decide whichsupport node (e.g. SGSN) of the selected operator is to be used forattachment or connection (e.g. signalling connection and/or user trafficconnection). A signalling connection can be provided for transferringmessages such as L3 messages, e.g. MM and SM, between a network elementsuch as a user equipment, e.g. MS, and the support node. Hence, theaccess network element may be alternatively connected to differentsupport nodes serving e.g. the same area, e.g. routing area.

In accordance with the invention, area identifiers such as “Routing AreaIdentity (RAI)” of different operators may be used by the user equipmentor access network element (e.g. RNC) to detect or derive a list ofalternatively selectable operators. In this list different support nodesof the operators may be identified by their addresses. This list may bepreconfigured inside the RNC.

Basically, for RAN sharing, the UE is able to indicate to which corenetwork it wants to connect to. The UE can do that because it will beinformed on which core networks are available. The UE can detect theavailable core networks e.g. by deriving the available mobile networkcodes from the broadcasted RAI or LAI. The UE then may send the selectedmobile network code to the RNC/BSC in order to get connected to theselected core network.

It may be possible that both 2G and 3G core networks are available. Thisis the case e.g. in GERAN, where it is possible to connect either to a2G or 3G core network from one cell. In order to select the appropriatecore network (2G or 3G), the RNC/BSC should also indicate which corenetworks are 2G and which are 3G. This is possible by specifying thebroadcasted RAIs or LAIs as information which is only read or readableby 2G UEs or by 3G UEs. As an alternative, the RNC/BSC could broadcast2G/3G information together with a RAI or LAI, but in this case, thebroadcast information is increased.

This implementation of the invention uses the RAI/LAI information toderive the available mobile network codes.

As another alternative only one type of broadcast is sent to UE (both 2Gand 3G) and the RNC then recognizes if an incorrect type of UE tries toattach to an inappropriate type of CN. The RNC then corrects theinformation and overrides the choice of the UE.

The derivation of Mobile Network Codes (mncs) from RAIs is one possiblesolution alternative.

MS is informed on which interfaces are supported by each operator. Andclearly only A/Gb capable MS can not access CN through Iu interface.

New 2G LAIs/RAIs may be added to new SI (System Information) messagesthat only new MS will read.

The proposed solutions are able to provide RAN sharing in GERAN.Moreover the invention can be applied elsewhere as in RAN sharing.

FIGS. 2 to 5 show different embodiments for implementing RAN sharing bymultiple networks, e.g. CN operators OP_A, OP_B, OP_C.

The CN operators OP_A, OP_B, OP_C comprise at least one support node,e.g. SGSN or MSC, connected to the RAN, e.g. to RNC 3. In theillustrated embodiments, two support nodes SGSN1, SGSN2, SGSN3, SGSN4,SGSN5, SGSN6, preferably of different types such as second generationtype (2_G) or third generation type (3_G) of each CN operator OP_A,OP_B, OP_C are shown to provide a pool 10.

Each CN operators OP_A, OP_B, OP_C has its own identifier “mnc41”,“mnc42”, “mnc43” (mnc, mobile network code),as shown in the drawings.Further, each CN operators OP_A, OP_B, OP_C comprises, in thisembodiment, two support nodes SGSN1, SGSN2; SGSN3, SGSN4; SGSN5, SGSN6,but may of course include only one or more than two support entities.

FIG. 2 shows another way of RAN sharing by multiple CN operators.Location areas and routing areas are configured by the RAN operator.

According to FIG. 2, the network(s) are broadcasting not onlyidentifiers, e.g mnc41, mnc42, mnc43, of the operator networks but alsoadditional identifiers nri (nri1 to nri6) (nri=Network ResourceIdentifier) for identifying the support nodes (SGSN1 to SGSN6) of therespective networks. Thus, the information mnc41 nri1, nri2; mnc42 nri3,nri4; mnc43 nri5, nri6 is broadcast and received by the UEs 2 (step 1).

Step 2: UE 2 selects, in accordance with internal selection criteriasuch as the criteria mentioned above, e.g. mnc42 and sends theidentifier nri3 to RNC 3.

Step 3: RNC 3 derives the operator code mnc42 from the receivedidentifier nri3 and selects a CN node based on mnc42 and eventuallybased on nri3. If available and e.g. not overloaded, RNC 3 may selectSGSN3 defined by the identifier nri3.

However, RNC 3 may also be designed to freely select any other availablesupport entity of the operator network OP_B defined by the derived mnccode, for supporting the UE 2. Thus, in the latter case, either SGSN3 orSGSN4 can be selected. In this example SGSN 4 is chosen.

This alternative of free selection of a support entity for the UE 2likewise applies to all other embodiment. The selection of an availablesupport entity from the operator network defined by the identifierreceived by the RNC 3, e.g. nri or mnc, may be based on a selectioncriteria such as optimum distribution of actual support entities load,etc. The selection criteria may be contained in a selection criteriatable or algorithm available to the RNC 3 or provided internally in theRNC.

Step 4: The selected support entity SGSN4 sends its identifier nri4 tothe UE 2.

FIG. 3 shows an embodiment for providing RAN sharing in case of CNoperators of different type or generation such as 2G/3G CN operators.The operator OP_A is of second generation type (2G) whereas theoperators OP_B and OP_C are of third generation type (3G).

With this embodiment, 2G and 3G UEs can always select the appropriatecore network (2G or 3G).

The operator OP_A (mnc41, 2G) comprises support entities SGSN1 and SGSN2and is identified by (mnc41, 2G). The operators OP_B, OP_C comprisesupport entities SGSN3, SGSN4, and SGSN5, SGSN6, and are identified bythe codes mnc42, and mnc 43, respectively (mnc42, 3G), (mnc43, 3G).

The RAN includes a BSC (Base Station Controller) 11 which broadcastsRAIs (Routing Area Identities). The broadcasted RAIs are sent with anidentifier or frequency or other coding so as to distinguish between 2Gand 3G information. Preferably, two types of IEs (Information Elements)are introduced which are broadcast for identifying the type of supportnode: IEs for 2G and 3G.

One or more Network Resource Identifiers (nri) is allocated to a CNnode.

Step 1: The RAN (BSC 11) is broadcasting only for 2G UE:

-   -   OP_A_RAI,        and only for 3G UE:    -   OP_B_RAI    -   OP_C_RAI.

Step 2: UE 2 supports, in this example, 2G, reads only 2G information,i.e. OP_A_RAI. RAI consists of mobile country code, mobile network codeand routing area code, so UE 2 is able to select the mobile network codemnc41 from OP_A_RAI. The UE 2 sends this mobile network code mnc41 tothe RAN.

Step 3: BSC 11 selects based on mnc41 one of the CN nodes SGSN1, SGSN2.

Step 4: The selected SGSN2 sends its identifier nri2 to the UE 2. _Inthe embodiment of FIG. 4, similar to FIG. 3, RAN sharing is providedwith different 2G/3G CN operators.

Step 1: The RAN is broadcasting per a cell belonging to a location areaor routing area only for 2G UE:

-   -   mnc41,        and only for 3G UE:    -   mnc42    -   mnc43.

Step 2: The UE 2 supports 2G, reads 2G information and selects the onlyoffered 2G identifier mnc41.

Step 3: The BSC 11 selects a CN node SGSN2 based on the identifier mnc41sent from the UE 2.

Step 4: The selected SGSN2 sends its identifier nri2 to the UE 2.

In the embodiment according to FIG. 5, RAN sharing is provided for 2G/3GCN operators. Generation information (2G/3G) is broadcast together withcore network operator information (mnc).

Step 1: The RAN is broadcasting mnc41 2G; mnc42 3G; and mnc43 3G.

Step 2: UE 2 supports 2G and therefore selects mnc41. The selectedidentifier mnc41 is sent to the BSC 11.

Step 3: BSC 11 selects based on mnc41 a CN node of OP_A, e.g. SGSN2.

Step 4: The selected SGSN2 sends its identifier nri2 to the UE 2.

Note that, for all embodiments, the further details regarding selectioncriteria, subsequent transmissions between UE 2 and the selected supportentity etc. may be identical or similar to the above described detailedexplanations.

The radio network controller or base station controller or DNS server 7or any other entity of the networks preferably comprises, or has accesspossibility to, a memory (not shown) storing lists (tables) of servingnodes available for alternatively covering routing areas or locationareas of the networks.

FIG. 6 shows an example of a table stored in the memory. According tothis example, the table contains several columns and rows. The leftcolumn “SGSN” lists the available serving nodes. SGSN1 may correspond toSGSN 4, SGSN2 may correspond to SGSN 6, and SGSN3, SGSN4 may correspondto SGSN 4′, SGSN 6′, or further serving nodes not shown in FIG. 1 andcovering other routing or location areas of the network 1. The tablefurthermore contains a column “IP address of SGSN” listing the IPaddresses of the individual available serving nodes. The column “Type ofSGSN” or “(SGSN identifier)” lists the identifiers identifying the typesof the individual serving nodes. In this example, the type of the node(2G or 3G) is represented by the identifier. The column “Routing Area”lists the routing areas or location areas being covered by theindividual serving nodes. As an example, the serving nodes SGSN1 SGSN2,SGSN3 and SGSN4 are available for covering the same first routing areaRA1 whereas the serving nodes SGSN1 SGSN2, SGSN3 and SGSN5 are availablefor alternatively covering a second routing area RA2 in which a mobilestation may be located, e.g. after moving thereto from routing area RA1.The table may be stored in the RAN or other control element forproviding the information on the generation type to be broadcast.

The support network elements may also be MSCs (Mobile Switching Centres)or other types of serving elements, e.g. in circuit-switched networks.

The solutions provided by the present invention are preferablyapplicable in a case where network elements of different generation(such as 2G SGSN and a 3G SGSN) are provided which handle theconnections for the same area, e.g. routing area. The selection of thesupport node may be made depending on the type of the connectionestablished and/or requested, or on the type of the user equipment. Asan example, the invention may be employed in a GERAN system (GSM/EDGEradio access network).

The present invention allows an effective adaptation of a cellularnetwork being at least partly e.g. IP-based. IP networks are essentiallypeer-to-peer structured whereas the conventional cellular networks suchas GSM, UMTS, etc. are typically based on an hierarchical architecturewherein a radio access network (RAN) or, in more detail, a controllercontrolling the radio access such as a RNC, RNS, BTS, BSS and the like,is handled by a single serving node (e.g. MSC/VLR; SGSN; . . . ).

The invention generally proposes a structure and method wherein onenetwork element providing e.g. radio access (e.g. RAN) to a userequipment is connected to many serving nodes such as core network (CN)nodes. This reduces the number of inter-CN-node-area update proceduresand increases the reliability. The invention hence proposes a newarchitecture for a cellular system wherein one radio access network (orthe network element providing or controlling the radio access) as wellas a location area (LA) or routing area (RA) can be handled by manyserving nodes of the same or different type. A routing function fordeciding to which serving node the connection is to be made, ispreferably located in the radio access network (RAN) or the respectivenetwork element providing or controlling the radio access. The routingfunction located in the RAN additionally provides or comprises a methodfor selection of the serving node to connect to.

This method and structure can be used by the radio access network (orRAN controlling node or component) to find the serving node to be used.

In accordance with one aspect of the invention, a user equipment such asa MS may be adapted to select an operator.

The method and system according to the invention may be used to allowmany operators (each owning their own serving node) to share a commonRadio Access Network (owned by another operator). If every operator usesa different CN identifier, and if the MSs are configured to always usesame CN identifier (even in the very first attach request) based onsubscription information typically read from a SIM card, then the MSwill always be connected to an SGSN owned by this operator (from whichthey bought SIM card).

Although preferred embodiments have been described above, the inventionis not limited thereto and may also be implemented in networks ofdifferent types using serving nodes of different structure such asMSC/VLR.

1-16. (canceled)
 17. System for providing an attachment or a connectionin a communication network comprising a radio access network and atleast two operator networks, the system being adapted to route aconnection between a user equipment and another network element via theradio access network, and one or more of alternatively selectablesupport network elements of the operator networks, the radio accessnetwork being adapted to broadcast information on available operatornetworks or support network elements to the user equipment, wherein thebroadcast information includes information on the mobile generation typeof the operator network to which the support network element or elementsbelong, the user equipment being adapted to receive the broadcastinformation and to send selection information to the radio accessnetwork for selecting an operator network and/or a support networkelement, wherein the broadcast information includes area identifiers ofthe operator networks, the broadcast area identifiers being specified asinformation which is only readable by user equipments of the respectivegeneration type, and wherein the user equipment is adapted to receiveonly that part of the broadcast information which is intended for thegeneration type of the user equipment.
 18. System according to claim 17,wherein the area identifiers of the operator networks are Location orRouting Area Identifiers (RAIs).
 19. System according to claim 17,wherein the broadcast information includes mobile network codes of theoperator networks.
 20. System according to claim 17, wherein thebroadcast information includes mobile network codes of the operatornetworks, and identifiers for identifying available support networkelements.
 21. System according to claim 17, wherein the radio accessnetwork or selected operator network is adapted to select a supportnetwork element and send information on the selected support element tothe user equipment.
 22. System according to claim 17, wherein thesupport network elements are serving nodes, preferably SGSNs.
 23. Systemaccording to claim 17, wherein the radio access network includes a RadioNetwork Controller or a Base Station Controller.
 24. System according toclaim 17, wherein at least one of the network elements is adapted tostore a list of support network elements of the operator networks, saidlist identifying the types of support network elements.
 25. Method forproviding an attachment or a connection in a communication network,wherein a connection is routed between a user equipment and anothernetwork element via a radio access network, and one or more ofalternatively selectable support network elements of at least twooperator networks, the radio access network broadcasting information onavailable operator networks or support network elements to the userequipment, the broadcast information including information on thegeneration type of the support network elements, wherein the broadcastinformation includes area identifiers of the operator networks, thebroadcast area identifiers being specified as information which is onlyreadable by user equipments of the respective generation type, andwherein the user equipment receives only that part of the broadcastinformation which is intended for the generation type of the userequipment, and the user equipment sends selection information to theradio access network for selecting an operator network and/or a supportnetwork element.
 26. Method according to claim 25, wherein the broadcastarea identifiers of the operator networks are Location or Routing AreaIdentifiers (RAIs).
 27. Method according to claim 25, wherein thebroadcast information includes mobile network codes of the operatornetworks.
 28. Method according to claim 25, wherein the broadcastinformation includes mobile network codes of the operator networks, andidentifiers for identifying available support network elements. 29.Method according to claim 25, wherein the radio access network orselected operator network select a support network element and sendinformation on the selected support element to the user equipment. 30.Method according to claim 25, wherein the support network elements areserving nodes, preferably SGSNs.
 31. Method according to claim 25,wherein the radio access network includes a Radio Network Controller ora Base Station Controller.
 32. Method according to claim 25, wherein atleast one of the network elements stores a list of support networkelements of the operator networks, said list identifying the types ofsupport network elements.